JP2005240602A - Exhaust apparatus of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust apparatus of an internal combustion engine capable of preventing the disturbance of exhaust flow in an expansion chamber. <P>SOLUTION: This exhaust apparatus of the internal combustion engine 1 comprises the expansion chamber 8 into which exhaust gases exhausted from cylinders are collected, a plurality of branch pipes 4 to 7 leading the exhaust gases from the exhaust ports of the cylinders into the expansion chamber 8, a catalyst 3 positioned on the exhaust gas downstream side of the expansion chamber 8 and purifying the exhaust gases led through the outlet part 11 of the expansion chamber. The branch pipes 4 to 7 are connected to the expansion chamber 8 so that the exhaust flows flowing from one side opening parts 4a to 7a of the branch pipes 4 to 7 into the expansion chamber 8 are directed in roughly a same direction and are not directed to the outlet part 11 of the expansion chamber. The expansion chamber 8 is formed at a position where the opening center P of the outlet part 11 of the expansion chamber is orthogonal to the direction of a cylinder row and comes out of a plane including a cylinder row center Q. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust device for an internal combustion engine.

  Patent Document 1 discloses a configuration in which exhaust from each cylinder is introduced into an expansion chamber so that exhaust flows between the cylinders interfere with each other.

In this Patent Document 1, at the time of cold start, the ignition timing is retarded to raise the temperature of the exhaust, oxidize unburned hydrocarbons, and promote early activation of the catalyst.
JP 2002-122017 A

  However, in Patent Document 1, since the ignition timing is retarded in order to raise the exhaust gas temperature at the time of cold start, the exhaust gas volume increases. The exhaust manifold wall surface is in a cold state immediately after starting.

  Therefore, if exhaust flows from each cylinder collide with each other in the expansion chamber and interfere with each other, the turbulence of the exhaust flow in the expansion chamber increases, resulting in heat dissipation due to a larger heat transfer coefficient to the expansion chamber wall. May occur, and the exhaust gas temperature may fall, and the temperature rise effect of the exhaust gas in the exhaust manifold may be reduced. Moreover, there is a possibility that the output may be reduced due to cylinder interference in the expansion chamber.

  Therefore, the present invention is located in the expansion chamber where the exhaust discharged from each cylinder gathers, a plurality of branch pipes for introducing the exhaust from the exhaust port of each cylinder into the expansion chamber, and the exhaust downstream side of the expansion chamber, And an exhaust device for an internal combustion engine having a catalyst for purifying exhaust gas introduced through the expansion chamber outlet, and the branch pipes have substantially the same exhaust flows flowing into the expansion chamber from the one end side opening of each branch pipe. The expansion chamber is connected to the expansion chamber so as to be directed in the same direction and not toward the expansion chamber outlet, and the expansion chamber has a plane in which the opening center of the expansion chamber outlet is perpendicular to the cylinder row direction and includes the cylinder row center. It is characterized by being formed at a position off the top.

  According to the present invention, the residence time of the exhaust gas that has flowed into the expansion chamber and does not directly escape to the outlet portion of the expansion chamber and stays in the expansion chamber is relatively increased. Can be efficiently oxidized, and exhaust performance can be improved. In addition, the exhaust flows from the branch pipes do not collide with each other in the expansion chamber, and the increase in the heat transfer coefficient from the exhaust in the expansion chamber to the expansion chamber wall, which increases due to the disturbance of the exhaust flow in the expansion chamber, is suppressed. In general, the exhaust temperature can be prevented from lowering. Further, cylinder interference in the expansion chamber can also be prevented, so that a reduction in engine output due to cylinder interference can be reduced.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front view showing a schematic configuration of an exhaust device for an internal combustion engine according to a first embodiment of the present invention, and FIG. 2 is a right side view of FIG. In addition, this embodiment shows the example applied to the inline 4-cylinder engine.

  The exhaust device 1 is generally composed of an exhaust manifold 2 connected to an exhaust port (not shown) of an engine body (not shown), and a catalyst 3 connected to the exhaust manifold 2, and the exhaust device 1 is arranged laterally. In this layout, the exhaust manifold 2 is located at the bottom, and the catalyst 3 is disposed below the exhaust manifold 2 (downward in FIGS. 1 and 2).

  The exhaust manifold 2 is connected to the branch pipes 4, 5, 6, 7 communicating with the exhaust ports of the respective cylinders and one end sides of the branch pipes 4, 5, 6, 7, and joins the exhaust discharged from the cylinders. And an expansion chamber 8.

  One end of each branch pipe 4, 5, 6, 7 is connected to the outer peripheral wall of the expansion chamber 8. The other ends of the branch pipes 4, 5, 6, and 7 are connected to each other by an elongated rectangular plate-like flange 9. By fixing the flange 9 to the engine body, the exhaust upstream side end portion of the exhaust manifold 2 is connected. The other end sides of the branch pipes 4, 5.6, and 7 that are 10 are connected to the corresponding exhaust ports. The passage cross-sectional areas of the branch pipes 4, 5, 6, and 7 are equal to each other.

  The expansion chamber 8 has an expansion chamber outlet 11 on the exhaust downstream side (downward in FIGS. 1 and 2). The catalyst 3 is connected to the exhaust downstream end 12 of the exhaust manifold 2 located on the exhaust downstream side of the expansion chamber outlet 11.

  As shown in FIG. 3, each branch pipe 4, 5, 6, 7 has each exhaust gas flowing into the expansion chamber 8 from one end side opening 4 a, 5 a, 6 a, 7 a of each branch pipe 4, 5, 6, 7. The flows are respectively connected to the expansion chambers 8 so as to be directed in substantially the same direction. In other words, one end side opening 4a of each branch pipe 4, 5, 6, 7 so that the exhaust flows flowing into the expansion chamber 8 from each branch pipe 4, 5, 6, 7 do not interfere with each other. , 5a, 6a, 7a are connected to the expansion chamber 8 so that the vortex f5 of the exhaust flow is formed in the expansion chamber 8 so that the opening directions thereof are substantially in the same direction. Has been. That is, each branch pipe 4, 5, 6, 7 is opened at one end so that the flow vectors of the exhaust flows f1 to f4 flowing into the expansion chamber 8 from the branch pipes 4, 5, 6, 7 substantially coincide with each other. The opening directions of the portions 4a, 5a, 6a, and 7a are directed in substantially the same direction.

  Furthermore, each branch pipe 4, 5, 6, 7 is connected to the expansion chamber 8 so that the one end side openings 4 a, 5 a, 6 a, 7 a do not face the expansion chamber outlet 11. The expansion chamber 8 is formed such that the opening center P of the expansion chamber outlet 11 is not positioned on a plane that is orthogonal to the cylinder row direction and includes the cylinder row center. In other words, the opening center P of the expansion chamber outlet 11 is offset with respect to the cylinder row center Q. Here, the cylinder row center Q substantially coincides with an intermediate position between the other end side opening 4b of the branch pipe 4 and the other end side opening 7b of the branch pipe 7 in the cylinder row direction (left and right direction in FIG. 3). It is.

  The branch pipes 4, 5, 6, and 7 extend from the branch pipes 4, 5, 6, and 7 at the one end side openings 4a, 5a, 6a, and 7a of the branch pipes 4, 5, 6, and 7, respectively. The inner wall surface of the branch pipe on the inflow direction side (the left side in FIG. 3) of the exhaust gas flowing into the inner space 8 is formed so as to be smoothly continuous with the inner wall surface of the expansion chamber 8.

  Further, the exhaust passage cross-sectional area A <b> 2 at the expansion chamber outlet portion 11 is formed to be smaller than the exhaust passage cross-sectional area in the expansion chamber 8 on the exhaust upstream side of the expansion chamber outlet portion 11. More specifically, the passage cross-sectional area A2 at the expansion chamber outlet 11 is set to be not more than twice the passage cross-sectional area A1 of each branch pipe 4, 5, 6, 7.

  The expansion chamber 8 is formed in a substantially funnel shape in the vicinity of the expansion chamber outlet 11 so that the cross-sectional area of the passage gradually decreases toward the expansion chamber outlet 11 on the exhaust downstream side. The exhaust manifold 2 is formed in a substantially funnel shape so that its passage cross-sectional area gradually increases from the expansion chamber outlet portion 11 toward the exhaust downstream side end portion 12 of the exhaust manifold 2. That is, the exhaust manifold 2 has a shape in which the passage cross-sectional area is restricted before and after the expansion chamber outlet portion 11.

  An air-fuel ratio sensor 13 for detecting the air-fuel ratio in the exhaust is disposed at the position of the expansion chamber outlet 11 of the exhaust manifold 2.

  In such a first embodiment, the exhaust flows flowing into the expansion chamber 8 from the one end side openings 4a, 5a, 6a, 7a of the branch pipes 4, 5, 6, 7 are directed in substantially the same direction. At the same time, the one end side openings 4a, 5a, 6a, and 7a of the branch pipes 4, 5, 6, and 7 are not directly directed to the expansion chamber outlet portion 11, and the opening center P of the expansion chamber outlet portion 11 is in the cylinder row direction. Since the exhaust gas flowing into the expansion chamber 8 does not directly escape to the expansion chamber outlet 11 and stays in the expansion chamber 8 is configured so as not to be positioned on a plane that is orthogonal to the cylinder row center Q. As a result, the unburned hydrocarbons in the exhaust in the expansion chamber 8 can be efficiently oxidized, and the exhaust performance can be improved. Further, the exhaust flows flowing into the expansion chamber 8 from the branch pipes 4, 5, 6, 7 are directed in substantially the same direction, so that they do not collide with each other in the expansion chamber 8, and the vortex flows into the expansion chamber 8. In the expansion chamber 8, the exhaust flows f1, f2, f3, and f4 from the branch pipes 4, 5, 6, and 7 do not collide with each other in the expansion chamber 8. The increase in the heat transfer coefficient from the exhaust in the expansion chamber 8 to the inner wall of the expansion chamber 8 that increases due to the turbulence of the exhaust flow can be suppressed, and the exhaust temperature can be generally prevented from decreasing. Further, cylinder interference in the expansion chamber 8 can also be prevented, so that a reduction margin of engine output due to cylinder interference can be reduced.

  Further, the branch pipes 4, 5, 6, and 7 extend from the branch pipes 4, 5, 6, and 7 at the one end side openings 4a, 5a, 6a, and 7a of the branch pipes 4, 5, 6, and 7, respectively. Since the inner wall surface of the branch pipe on the inflow direction side (the left side in FIG. 3) of the exhaust gas flowing into the inner wall 8 is formed to be smoothly continuous with the inner wall surface of the expansion chamber 8, each branch pipe 4, 5, 6, 7 is formed. When the exhaust gas flows into the expansion chamber 8 from the exhaust gas, the exhaust gas flows into the expansion chamber 8 along the inner wall surface of the expansion chamber 8 without colliding with the inner wall surface of the expansion chamber 8. It is advantageous for reducing the heat transfer coefficient to the wall surface, and is also advantageous for forming an exhaust flow (flow f5 in FIGS. 1 to 3) that vortexes in the expansion chamber 8.

  Since the exhaust manifold 2 has a shape in which the passage cross-sectional area is throttled before and after the expansion chamber outlet portion 11, the residence time of the exhaust gas in the expansion chamber 8 becomes relatively long, and the expansion chamber 8 It is possible to further promote the oxidation of unburned hydrocarbons in the interior, and to send a uniform flow of exhaust to the catalyst 3, thereby improving the conversion efficiency in the catalyst 3.

  In addition, since the air-fuel ratio sensor 13 is disposed at the position where the exhaust manifold 2 is throttled, that is, at the expansion chamber outlet 11, the variation in sensing between cylinders can be avoided.

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the element same as 1st Embodiment mentioned above, and the overlapping description is abbreviate | omitted.

  The exhaust device 2 in the second embodiment is roughly constituted by the exhaust manifold 2 and the catalyst 3 positioned on the exhaust downstream side of the exhaust manifold 21 as in the first embodiment described above. The positional relationship between the exhaust manifold 2 and the catalyst 3 located in the direction is different from that of the first embodiment.

  That is, as shown in FIGS. 4 to 6, the catalyst 3 is not positioned below the exhaust manifold 2 with respect to the exhaust manifold 2 positioned on the side of the engine main body (not shown). It is located on the side of the exhaust manifold 2 (the right side in FIGS. 4 and 5).

  Also in the second embodiment, as in the first embodiment described above, the branch pipes 4, 5, 6, 7 are provided on the one end side openings 4 a, 5 a of the branch pipes 4, 5, 6, 7. , 6a, 7a, the exhaust flows f1, f2, f3, f4 flowing into the expansion chamber 8 are respectively connected to the expansion chamber 8 so as to be directed in substantially the same direction. The one end side openings 4a, 5a, 6a, and 7a are directed in substantially the same direction so that the flow vectors of the exhaust flows f1 to f4 flowing into the expansion chamber 8 coincide with each other. Furthermore, each branch pipe 4, 5, 6, 7 is connected to the expansion chamber 8 so that its one end side openings 4a, 5a, 6a, 7a are not directed to the expansion chamber outlet portion 11, respectively. The opening center P of the expansion chamber outlet 11 is formed so as not to lie on a plane perpendicular to the cylinder row direction and including the cylinder row center Q. The branch pipes 4, 5, 6, and 7 extend from the branch pipes 4, 5, 6, and 7 at the one end side openings 4a, 5a, 6a, and 7a of the branch pipes 4, 5, 6, and 7, respectively. The inner wall surface of the branch pipe on the inflow direction side (the left side in FIG. 6) of the exhaust gas flowing into 8 is formed so as to be smoothly continuous with the inner wall surface of the expansion chamber 8. Further, the exhaust passage cross-sectional area A <b> 2 at the expansion chamber outlet portion 11 is formed to be smaller than the exhaust passage cross-sectional area in the expansion chamber 8 on the exhaust upstream side of the expansion chamber outlet portion 11. More specifically, the passage cross-sectional area A2 at the expansion chamber outlet 11 is set to be not more than twice the passage cross-sectional area A1 of each branch pipe 4, 5, 6, 7. The exhaust manifold 2 has a shape in which the passage cross-sectional area is narrowed before and after the expansion chamber outlet portion 22, and the air-fuel ratio sensor 13 that detects the air-fuel ratio in the exhaust includes an expansion chamber of the exhaust manifold 2. It is arranged at the position of the outlet 11.

  Therefore, also in the exhaust apparatus 21 in this 2nd Embodiment, the effect similar to the exhaust apparatus 1 of 1st Embodiment mentioned above can be acquired.

The technical idea of the present invention that can be grasped from the above embodiment will be listed together with the effects thereof.
(1) An exhaust system for an internal combustion engine includes an expansion chamber in which exhaust discharged from each cylinder gathers, a plurality of branch pipes for introducing exhaust from the exhaust ports of each cylinder into the expansion chamber, and an exhaust downstream side of the expansion chamber And a catalyst for purifying exhaust gas introduced through the expansion chamber outlet, and each branch pipe has an exhaust flow flowing into the expansion chamber from one end side opening of each branch pipe, The expansion chambers are connected to the expansion chambers so that they are oriented in substantially the same direction and not to the expansion chamber outlet, and the expansion chamber has an opening center of the expansion chamber outlet perpendicular to the cylinder row direction and the cylinder row center. It is formed at a position deviating from the plane that contains it. As a result, the residence time of the exhaust gas that has flowed into the expansion chamber and does not directly escape to the expansion chamber outlet and stays in the expansion chamber is relatively increased, and oxidation of unburned hydrocarbons in the exhaust in the expansion chamber is reduced. This can be performed efficiently, and exhaust performance can be improved. In addition, the exhaust flows from the branch pipes do not collide with each other in the expansion chamber, and the increase in the heat transfer coefficient from the expansion chamber exhaust to the expansion chamber wall, which increases due to the disturbance of the exhaust flow in the expansion chamber, is suppressed. In general, the exhaust temperature can be prevented from lowering. In addition, cylinder interference in the expansion chamber can be prevented, so that a reduction margin of engine output due to cylinder interference can be reduced.

  (2) In the exhaust system for an internal combustion engine according to (1), the exhaust passage cross-sectional area at the outlet of the expansion chamber is smaller than the cross-sectional area of the exhaust passage in the expansion chamber upstream of the outlet of the expansion chamber. Is formed. As a result, the residence time of the exhaust in the expansion chamber becomes relatively long, the oxidation of unburned hydrocarbons in the expansion chamber can be further promoted, and a uniform flow of exhaust can be sent to the catalyst. The conversion efficiency with a catalyst can be improved.

  (3) In the exhaust system for an internal combustion engine according to (2), an air-fuel ratio sensor is disposed in the vicinity of the expansion chamber outlet. As a result, variations in sensing between cylinders can be avoided.

  (4) In the exhaust device for an internal combustion engine according to any one of the above (1) to (3), the inner wall surface of the branch pipe on the inflow direction side of the exhaust gas flowing from the branch pipe into the expansion chamber at the one end side opening of each branch pipe Are formed so as to be smoothly continuous with the inner wall surface of the expansion chamber. As a result, when exhaust flows into the expansion chamber from each branch pipe, the exhaust flows into the expansion chamber along the inner wall surface of the expansion chamber without colliding with the inner wall surface of the expansion chamber. This is advantageous in reducing the heat transfer coefficient to the indoor wall surface, and is also advantageous in forming an exhaust flow that vortexes in the expansion chamber.

The front view of the exhaust apparatus of the internal combustion engine in 1st Embodiment of this invention. The right view of FIG. The top view of the exhaust apparatus of the internal combustion engine in 1st Embodiment of this invention. The front view of the exhaust apparatus of the internal combustion engine in 2nd Embodiment of this invention. The right view of FIG. The top view of the exhaust apparatus of the internal combustion engine in 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exhaust device 2 ... Exhaust manifold 3 ... Catalyst 4 ... Branch pipe 5 ... Branch pipe 6 ... Branch pipe 7 ... Branch pipe 8 ... Expansion chamber 11 ... Expansion chamber exit part

Claims (4)

Located in the expansion chamber where the exhaust discharged from each cylinder gathers, a plurality of branch pipes for introducing the exhaust from the exhaust ports of each cylinder into the expansion chamber, and on the downstream side of the expansion chamber through the expansion chamber outlet In an exhaust system of an internal combustion engine having a catalyst for purifying the introduced exhaust,
Each branch pipe is connected to the extension chamber so that the exhaust flows flowing into the extension chamber from the one end side opening of each branch pipe are oriented in substantially the same direction and not in the extension chamber outlet,
The exhaust chamber of the internal combustion engine, wherein the expansion chamber is formed such that the center of the opening of the expansion chamber outlet is perpendicular to the cylinder row direction and deviates from a plane including the cylinder row center.   2. The internal combustion engine according to claim 1, wherein the cross-sectional area of the exhaust passage at the outlet portion of the expansion chamber is formed to be smaller than the cross-sectional area of the exhaust passage in the expansion chamber upstream of the outlet portion of the expansion chamber. Exhaust system.   The exhaust system for an internal combustion engine according to claim 2, wherein an air-fuel ratio sensor is disposed in the vicinity of the outlet of the expansion chamber.   The inner wall surface of the branch pipe on the inflow direction side of the exhaust gas flowing from the branch pipe into the expansion chamber is formed so as to be smoothly continuous with the inner wall surface of the expansion chamber at the one end side opening of each branch pipe. Item 4. An exhaust system for an internal combustion engine according to any one of Items 1 to 3.

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